1. Field of the Invention
This present invention is related to an integrated structure of an insulated gate bipolar transistor (IGBT) and a diode and a method of forming the same, and more particularly, to an integrated structure of an IGBT and a rectifier diode and a method of forming the same.
2. Description of the Prior Art
An IGBT is regarded as a composite structure combining a metal-oxide-semiconductor field effect transistor (MOSFET) and a bipolar junction transistor (BJT). By combining the MOSFET's characteristic of easy control with a gate electrode and the BJT's characteristic of low turn-on voltage drop, the IGBT is widely applied in a high voltage and high power application.
Conventionally, the IGBT is formed on a substrate by semiconductor manufacturing technology. Then the IGBT is electrically connected to an external diode for providing a rectifier function, so that the circuit component of IGBT and the diode component can be packaged in the same package structure. However, the structure, which includes IGBT connected to an external diode, has higher production cost, more complicated packaging, and is large in size, so it does not conform to a trend of high degree of integration for electronic components.
Therefore, integration of an IGBT and a diode in the same circuit structure has been developed in the industry, but it still faces several problems with existing integration methods and structures. For example, one integration method of a diode and an IGBT teaches forming a conventional IGBT structure on a front side of a semiconductor substrate. An emitter and a collector of an IGBT are mainly formed on the two opposite surfaces (a front side and a backside) of a wafer, and the operation voltages of the diode and the IGBT are different as the material thickness changes. Therefore, the wafer has to be thinned from the backside in to particular thickness range to provide required voltage and resistance. Doped regions and an electrode layer are then formed on the backside of the wafer. However, the thinner the thickness of the wafer is, the more difficult a delivery process in the apparatus for manufacturing doped regions is because the wafer tends to break. For an IGBT with a withstand voltage of 600 volts, the thickness of the wafer is thinned below 100 micrometers with the traditional integration method. With such a thin thickness, the wafer tends to break in an implantation process forming doped diode regions. Therefore, the current integration method suffers from low product yield, and the broken wafers may causes severe contaminations to the apparatus.
As a result, how to provide an integrated structure of an IGBT and a diode, for lower cost, higher component density, higher withstand voltage, higher reliability, and higher yield, is still a major issue.